Ram 4500 Back Up Light Bulb Size

The Ram 4500 back up light utilizes 7440, 921, and 1156 bulb sizes depending on the specific configuration of the lighting assembly. Data for the bulbs covers the range from 2011 to 2018.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2018	7440 (With Projector Headlamps)
2018	921 (Without Projector Headlamps)
2011-2012	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament wedge bulb (T20). 12V, 21W.	7440
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The Ram 4500 backup light specifications reference three distinct bulb types across the model's listed years: the 7440, 921, and 1156.
The 7440 and 1156 are both rated at 12V and 21W, making them equivalent in power draw despite differing in base type and physical form.
The 7440 is a T20 single-filament wedge bulb, while the 921 is a T15 wedge bulb rated at 12V and 16W, drawing less power than the 7440.
The 1156 uses a BA15s bayonet base, a twist-and-lock mounting style, which is physically incompatible with the wedge-style sockets used by the 7440 and 921.
All three bulb types conform to ANSI standards applicable in the US and Canada.
For the 2018 Ram 4500, the correct backup light bulb depends on the headlamp configuration: the 7440 applies to vehicles with projector headlamps, and the 921 applies to those without.
The T20 and T15 designations refer to the bulb's tubular form factor, with T20 being physically larger than T15, meaning the two wedge types are not interchangeable despite sharing the same base style.
The 2011-2012 Ram 4500 uses the 1156 bulb, which is not interchangeable with either the 7440 or the 921 due to its bayonet base.